Improved external quantum efficiency of 293 nm AlGaN UVB LED grown on an AlN template

Khan, M. Ajmal; Matsumoto, Takuma; Maeda, Noritoshi; Kamata, Norihiko; Hasegawa, Hideki

doi:10.7567/1347-4065/aaea6a

Cited by 31 publications

(46 citation statements)

References 23 publications

(77 reference statements)

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“…From the result, the estimated TDD for the AlN layer without the nucleation layer is around ∼4.0 × 10 9 cm −2 . The value is slightly higher than some reported AlN layers grown on sapphire with the nucleation layer (Susilo et al , 2020; Khan et al , 2018). This indicates that even without AlN nucleation, the AlN layer can be grown better.…”

Section: Resultscontrasting

confidence: 57%

Effect of nucleation layer thickness on reducing dislocation density in AlN layer for AlGaN-based UVC LED

Samsudin

Mohd-Yusuf

Zainal

et al. 2021

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Purpose The purpose of this study is to investigate the influence of AlN nucleation thickness in reducing the threading dislocations density in AlN layer grown on sapphire substrate. Design/methodology/approach In this work, the effect of the nucleation thickness at 5 nm, 10 nm and 20 nm on reducing the dislocation density in the overgrown AlN layer by metal organic chemical vapor deposition was discussed. The AlN layer without the nucleation layer was also included in this study for comparison. Findings By inserting the 10 nm thick nucleation layer, the density of the dislocation in the AlN layer can be as low as 9.0 × 108 cm−2. The surface of the AlN layer with that nucleation layer was smoother than its counterparts. Originality/value This manuscript discussed the influence of nucleation thickness and its possible mechanism in reducing dislocations density in the AlN layer on sapphire. The authors believe that the finding will be of interest to the readers of this journal, in particular those who are working on the area of AlN.

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Section: Resultscontrasting

confidence: 57%

Effect of nucleation layer thickness on reducing dislocation density in AlN layer for AlGaN-based UVC LED

Samsudin

Mohd-Yusuf

Zainal

et al. 2021

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“…In UVB LEDs and LDs, the efficiency droops under high current injection and poor hole injection conditions toward the MQWs, leading to relatively poor radiative recombination 4 , 8 . Consequently, the performance of the UVB LEDs has been deteriorated at RT 4 , 8 , 12 , 23 , 24 , as presented in Table 1 . A reasonable level of 3D hole generation has been successfully realised in the AlGaN/GaN UVC LED by polarisation effect, which is supported by the distribution of Al composition profile from p-AlGaN HSL to the p-GaN contact-layer 33 , 34 , 47 .…”

Section: Resultsmentioning

confidence: 99%

“…The results have been compared with the previously available sample-HK02 8 , in which uniform composition (non-graded) of Al in the p-AlGaN HSL and EBL has been used. All the reported values of light output powers in this work correspond to the total radiant flux from the UVB LEDs, which have been calibrated for the accurate performances of UVB LED devices 8 , 23 , 24 . To measure the light output power on the wafer under CW- and pulse-operation at RT, Si photodetector was set behind the test samples.…”

Section: Methodsmentioning

confidence: 99%

“… Sources References UVB LED structure Max. output power EQE Wavelength CNRS Brault et al 17 Sapphire/AlN/AlGaN-QD 0.25 mw @ 100 mA 0.15% @ 20 mA 305–320 nm Kansas State University Kim et al 18 Sapphire/AlN/AlGaN-QW/p-AlGaN (in-dot quick test) 1.8 mW @ 350 mA Un-known 290 nm 305 nm TU Berlin/FBH Enslin et al 19 Rass et al 20 Guttmann et al 21 Susilo et al 22 Sapphire/AlN/AlGaN-QW/p-GaN (in-dot quick test) 9 mW @ 20 mA 18 mW @ 500 mA 1–2% @ 20 mA 302 nm 310 nm Riken Khan et al 24 Khan et al 23 Khan et al 23 Khan et al 25 Khan et al 26 Khan et al 8 Khan et al 8 Sapphire/AlN/AlGaN-QW/p-AlGaN (in-dot quick test) 12.5 mW @ 130 mA 7.1 mW @ 180 mA 13 mW @ 130 mA 12 mW @ 140 mA 17 mW @ 150 mA 32 mW @ 170 mA 30 mW @ 220 mA 3.3% @ 20 mA 0.5% @ 20 mA 4.4% @ 30 mA 2.4% @ 20 mA 5.6% @ 30 mA 6.5% @ 30 mA 4.7% @ 30 mA 294 nm 310 nm 295 nm 310 nm 295 nm 300 nm 310 nm This work 40 mW @ 170 mA 9.6% @ 10 mA 304 nm …”

Section: Introductionmentioning

confidence: 99%

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Achieving 9.6% efficiency in 304 nm p-AlGaN UVB LED via increasing the holes injection and light reflectance

Khan

Maeda

Yun

et al. 2022

Sci Rep

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Crystal growth of eco-friendly, ultrawide bandgap aluminium gallium nitride (AlGaN) semiconductor-based ultraviolet-B (UVB) light-emitting diodes (LEDs) hold the potential to replace toxic mercury-based ultraviolet lamps. One of the major drawbacks in the utilisation of AlGaN-based UVB LEDs is their low efficiency of about 6.5%. The study investigates the influence of Al-graded p-type multi-quantum-barrier electron-blocking-layer (Al-grad p-MQB EBL) and Al-graded p-AlGaN hole source layer (HSL) on the generation and injection of 3D holes in the active region. Using the new UVB LED design, a significant improvement in the experimental efficiency and light output power of about 8.2% and 36 mW is noticed. This is accomplished by the transparent nature of Al-graded Mg-doped p-AlGaN HSL for 3D holes generation and p-MQB EBL structure for holes transport toward multi-quantum-wells via intra-band tunnelling. Based on both the numerical and experimental studies, the influence of sub-nanometre scale Ni film deposited underneath the 200 nm-thick Al-film p-electrode on the optical reflectance in UVB LED is investigated. A remarkable improvement in the efficiency of up to 9.6% and light output power of 40 mW, even in the absence of standard package, flip-chip, and resin-like lenses, is achieved on bare-wafer under continuous-wave operation at room temperature. The enhanced performance is attributed to the use of Al-graded p-MQB EBL coupled with softly polarised p-AlGaN HSL and the highly reflective 0.4 nm-thick Ni and 200 nm-thick Al p-electrode in the UVB LED. This research study provides a new avenue to improve the performance of high-power p-AlGaN-based UVB LEDs and other optoelectronic devices in III–V semiconductors.

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“…Furthermore, AlGaN-based ultraviolet-B LEDs (UVB-LEDs) have been attracting great attention since the implementation of the Minamata Convention on Mercury. There is much potential for such LEDs to be used in medical (e.g., cancer immunotherapy; treatment of psoriasis, vitiligo, and pemphigus vulgaris) and agricultural (e.g., plant growth under UVB lighting; production of phytochemicals in the green leaves of vegetables) applications [3][4][5][6][7]. For example, narrow-band (NB-UVB) emission therapy at 310 nm has been found to be more effective than broad-band (BB-UVB) therapy at 280-320 nm in the treatment of psoriasis and atopic dermatitis; furthermore, NB-UVB phototherapy with emission at 310 nm appears suitable for cancer therapy and skin cure therapy [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Observation of Highly Durable Silicone Resin for Encapsulating AlGaN-Based UVB Light-Emitting Diodes

Lai¹,

Liu²,

Liu

et al. 2021

Applied Sciences

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In this paper, we report an AlN-based ceramic lead frame (LF) with encapsulating silicone between the surface of an AlGaN-based ultraviolet-B light-emitting diode (UVB-LED) chip and a quartz glass cover; the light output power (LOP) of this structure was 13.8% greater than that of the corresponding packaging structure without encapsulating silicone. Another packaging structure in which the silicone fully filled the cavity of the AlN-based ceramic LF included covering with quartz glass; in this case, the enhancement of the LOP was 11.7%. Reliability tests performed over a period of 3500 h at a forward current (If) of 100 mA revealed that the LOPs of these two silicone-containing packaging types decreased to 45.3 and 48.6%, respectively, of their initial values. The different degradation rates of these UVB-LEDs were not, however, correlated with the appearance of cracks in the encapsulating silicone during long-term operation. Excluding any possible mechanisms responsible for degradation within the UVB-LED chips, we suggest that the hermetic cover should be removed to avoid the appearance of cracks. Moreover, the main mechanism responsible for the slow degradation rates of LOPs in these proposed packaging structures involves the encapsulated silicone, after cracks have appeared, undergoing further deterioration by the UVB irradiation.

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Improved external quantum efficiency of 293 nm AlGaN UVB LED grown on an AlN template

Cited by 31 publications

References 23 publications

Effect of nucleation layer thickness on reducing dislocation density in AlN layer for AlGaN-based UVC LED

Effect of nucleation layer thickness on reducing dislocation density in AlN layer for AlGaN-based UVC LED

Achieving 9.6% efficiency in 304 nm p-AlGaN UVB LED via increasing the holes injection and light reflectance

Observation of Highly Durable Silicone Resin for Encapsulating AlGaN-Based UVB Light-Emitting Diodes

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